well, if u are talking bout long term r.s, then shld take into consideration tat pple do change over time...some for e better, some for e worse..if for e worse, then..sigh..
after knowing a person for too long, u will tend to take it for granted tat e person wld b there for u...or even like ur family members, some pple wont take another second to flare their temper at...that cld b one flaw tat pple cant take...not being v nice to each other (bu ke qi) attitude...
its how much pple are willing to give n take, forgive n forget...
i guess?